The sandals usually consist of a molded material insole on which a molded material midsole is attached and press fitted. Midsoles usually have projections and cut which couple respectively with the corresponding cuts and projections on the underlying outsole. Midsoles can be multi-layers with the top layer with softer material and the bottom layer with a harder material. Midsole usually consist of shock absorbing material, such Polyurethane or Ethylene-Vinyl Acetate (EVA), which have soft and flexible shock absorbing characteristics. The insole, if not present, will mean that the wearer's foot will come in directly in contact with the midsole. If this is the case, a multilayer midsole provides for improvement over a single layer midsole. The opposing sides of the sole edge have shaped projecting flaps with one or more slots for the passage of the straps which form the upper consisting of bands which hold the foot at the ankle and metatarsal area of the foot. Said straps may be made of fabric, leather, synthetic fabric or imitation leather or in any other suitable material.
The outsole which can be single or multilayer is the bottom of the sandal and it attaches to the midsole of the sandal. Because the outsole is the part of the sandal that comes into contact with the ground is made of harden and durable material. The midsoles are designed to provide cushioning and shock absorption.
For sandals with Polyurethane or EVA insoles or midsoles, the straps are usually made of leather, cloth, or plastic straps. With the typical sandal, the straps generally go through pre-punched openings in the sole and are held in place via cement, plugs or other method. The sandal has straps that enter the sole through several pre-punched or molded holes, some in the front of the sandal and several in the rear. The straps on the sandal will wear against the soft materials of the sole around the pre-punched or molded holes after several uses of the sandals. Also with straps around the outside of the sandal this too may also wear any soft material in the insole and midsole areas.
It is desirable to prevent or minimize the strap from wearing out the insole or midsole materials.